DataGridView.CellToolTipTextNeeded Event


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Occurs when a cell's ToolTip text is needed.

Namespace:   System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

public event DataGridViewCellToolTipTextNeededEventHandler CellToolTipTextNeeded

The CellToolTipTextNeeded event occurs only when the DataGridView control DataSource property is set or its VirtualMode property is true.

When you handle the CellToolTipTextNeeded event, the ToolTip text you specify in the handler is shown whenever the mouse pointer is over a cell and the control ShowCellToolTips property value is true. The CellToolTipTextNeeded event is useful when you want to display ToolTips determined by the current state or value of a cell.

The CellToolTipTextNeeded event also occurs whenever the value of the DataGridViewCell.ToolTipText property is retrieved, either programmatically or when the mouse pointer enters a cell.

You can use the DataGridViewCellEventArgs.ColumnIndex and RowIndex properties to determine the state or value of a cell, and use this information to change or modify the DataGridViewCellToolTipTextNeededEventArgs.ToolTipText property. This property is initialized with the value of the cell ToolTipText property, which the event value overrides.

Handle the CellToolTipTextNeeded event when working with large amounts of data to avoid the performance penalties of setting the cell ToolTipText value for multiple cells. For more information, see Best Practices for Scaling the Windows Forms DataGridView Control.

For more information about handling events, see NIB: Consuming Events.

The following code example demonstrates how to use a CellToolTipTextNeeded event handler to display information from hidden columns in a data-bound DataGridView control.

void dataGridView1_CellToolTipTextNeeded(object sender,
    DataGridViewCellToolTipTextNeededEventArgs e)
    string newLine = Environment.NewLine;
    if (e.RowIndex > -1)
        DataGridViewRow dataGridViewRow1 = dataGridView1.Rows[e.RowIndex];

        // Add the employee's ID to the ToolTipText.
        e.ToolTipText = String.Format("EmployeeID {0}:{1}",
            dataGridViewRow1.Cells["EmployeeID"].Value, newLine);

        // Add the employee's name to the ToolTipText.
        e.ToolTipText += String.Format("{0} {1} {2}{3}",

        // Add the employee's title to the ToolTipText.
        e.ToolTipText += String.Format("{0}{1}{2}",
            newLine, newLine);

        // Add the employee's contact information to the ToolTipText.
        e.ToolTipText += String.Format("{0}{1}{2}, ",
            dataGridViewRow1.Cells["Address"].Value.ToString(), newLine,
        if (!String.IsNullOrEmpty(
            e.ToolTipText += String.Format("{0}, ",
        e.ToolTipText += String.Format("{0}, {1}{2}{3} EXT:{4}{5}{6}",
            newLine, dataGridViewRow1.Cells["HomePhone"].Value.ToString(),
            newLine, newLine);

        // Add employee information to the ToolTipText.
        DateTime HireDate =
        e.ToolTipText +=
            String.Format("Employee since: {0}/{1}/{2}{3}Manager: {4}",
            HireDate.Month.ToString(), HireDate.Day.ToString(),
            HireDate.Year.ToString(), newLine,

.NET Framework
Available since 2.0
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